Salmon Fillet Intake Led to Higher Serum Triacylglycerol in Obese Zucker Fa/Fa Rats But Not in Normolipidemic Long-Evans Rats

Abstract

The triacylglycerol lowering effect of fatty fish and fish oils is well recognized, however we recently showed that salmon intake resulted in higher serum triacylglycerol concentration in obese Zucker fa/fa rats. Since effects of salmon fillet have never before been studied in rats, the objective of this study was to compare effects of salmon intake on serum lipids in hyperlipidemic obese rats with normolipidemic lean rats. Zucker fa/fa rats and Long-Evans rats were fed diets with 25% protein from baked salmon fillet and 75% protein from casein, or casein as sole protein source (control group) for four weeks. Serum triacylglycerol concentration was higher, and cholesterol and apolipoproteinB-100 concentrations were lower in Zucker fa/fa rats fed Baked Salmon Diet compared to Zucker fa/fa rats fed Control Diet, with no differences in serum triacylglycerol, cholesterol and apolipoproteinB-100 between Long-Evans rats fed Baked Salmon Diet or Control Diet. Serum triacylglycerol fatty acid composition showed greater similarities to dietary fatty acids in Zucker fa/fa rats than in Long-Evans rats. To conclude, intake of baked salmon fillet resulted in higher serum triacylglycerol concentration and lower serum cholesterol concentration in hyperlipidemic obese Zucker fa/fa rats but did not affect serum lipids in normolipidemic lean Long-Evans rats.

Urine and plasma concentrations of amino acids and plasma vitamin status differ, and are differently affected by salmon intake, in obese Zucker fa/fa rats with impaired kidney function and in Long-Evans rats with healthy kidneys

“…We propose that the higher plasma and urine concentrations of 1-MeHis and 3-MeHis in Zucker fa/fa rats fed the baked salmon diet are probably a result of salmon intake, and not degradation of muscle proteins. This suggestion is supported by similar growth patterns in the two dietary groups and the reported lower serum aspartate aminotransferase concentration in the baked salmon group in the Zucker fa/fa rat experiment (31) . Similarly, we propose that the higher urine concentrations of 1-MeHis and 3-MeHis in Long-Evans rats fed the baked salmon diet compared with the control diet originated from the fish intake.…”

“…Circulating concentrations of many compounds, including vitamin A (51) and 4-pyridoxic acid (52) , have been shown to be markedly elevated in patients with uraemic syndrome caused by compromised renal function, which agrees with the higher serum carbamide concentration observed in Zucker fa/fa rats compared with Long-Evans rats in the present study. Additionally, slower clearance of chylomicrons in Zucker fa/fa rats (53) leads to a longer circulation time for vitamins obtained from diets, and this is in accordance with the higher circulating concentrations of lipids in Zucker fa/fa rats compared with Long-Evans rats (31) and may, at least partially, explain the higher plasma vitamin concentrations in Zucker fa/fa rats.…”

“…Therefore, no power analysis has been conducted for the present study. We have shown that a group size of six rats was sufficient to distinguish between Zucker fa/fa rats and Long-Evans rats in regard to lipid metabolism (31) , and in a previous study in Zucker fa/fa rats we have shown that six rats per group was sufficient to detect differences in amino acid composition between a group fed cod protein and a control group (17) . Therefore, we found it worth looking into differences in amino acid compositions in plasma and urine as well as vitamin status between Zucker fa/fa rats and Long-Evans rats after salmon feeding.…”

“…We found that Zucker fa/fa rats had a higher concentration of glutathione, both in its oxidised and reduced forms, and lower concentrations of its precursors methionine, homocysteine, cystathionine, cysteine and glycine in plasma compared with Long-Evans rats. This suggests that in Zucker fa/fa rats, the endogenous synthesis of the powerful antioxidant, glutathione, is upregulated, possibly to counteract and prevent lipid peroxidation in these hyperlipidaemic rats (31,41) and/or as a consequence of disturbances in antioxidant defence systems as kidney function deteriorates (42) .…”

“…The experiments were initially designed to investigate the metabolic differences between the strains and to investigate the effects of intake of baked salmon on lipid metabolism in a rat model with reduced renal function (Zucker fa/fa rats) and in a rat model with normal renal function (Long-Evans rats). Results showing that the strains were significantly different in regard to lipid metabolism and that baked salmon intake affected lipid metabolism differently in these two rat models with six rats per group have been published (31) . In the present study, we wanted to study additional biomarkers in the same setting.…”